A new report from Kantar Worldpanel ComTech reveals Apple maintaining strong market share for its iOS mobile platform in the U.S., and that at both AT&T and Verizon, the iPhone remains king. For the 12 week period at the end of the year, iOS maintained a 51.2 percent market share, versus 44.2 percent for Android. RIM’s market share for its BlackBerry OS dropped from 6.1 percent to 1.1 percent.

“Apple’s continual improvement is thanks to both the iPhone 5 and older models attracting various customer groups, from repeat Apple buyers, first time smartphone buyers and those coming from other smartphone brands,” said Kantar Worldpanel ComTech analyst Mary-Ann Parlato.

“In particular, 36% of iOS sales were derived from other smartphone users over the last year. While this figure remains stable over time, the proportion of Android users moving towards the Apple brand increases. 19% of iOS sales over the last year were derived from Android users, compared to 9% in 2011,” continued Parlato.

Apple’s dominance is particularly noticeable at AT&T where Apple’s platform’s market share reached 74.7 percent of sales. But iOS also grew at Verizon, as well, reaching 58.8 percent in the report’s 12-week period of 2012, versus 38.5 percent for Android, a drop from 47.5 percent during the same period of 2011.

Microsoft Windows market share barely ticked up, 2.06 percent in 2012, versus 2.2 percent during the same time period at the end of 2011.